Imaging stretcher

ABSTRACT

A stretcher includes an elongated base having a head end and a foot end, a plurality of floor-engaging casters rotatably mounted to the base, a radiolucent upper deck, head and foot end hydraulic cylinders coupled to the base adjacent to the head and foot ends thereof, and head and foot end connectors for coupling the head and foot end hydraulic cylinders to the head and foot ends of the upper deck. The head and foot end connectors secure the upper deck to the base while allowing (a) movement of the upper deck between a low position and a high position, (aa) translation of the upper deck toward the foot end of the base, and (aaa) rotation of the upper deck to a Trendelenberg position or to a reverse Trendelenberg position. The head end and foot end hydraulic cylinders are spaced apart to define a central imaging region above the base between the hydraulic cylinders which is free of structure that would interfere with imaging.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention generally relates to a hospital stretcher. Moreparticularly, the present invention relates to an imaging stretcherwhich lends itself to fluoroscopy imaging.

Fluoroscopy imaging with a C-Arm is used by caregivers for diagnosticand surgical visualization. Many conventional imaging tables havedesigns based on operating room tables. Often these tables are of acantilever design where the support surface extends out from a singlesupport column. Such tables usually have all electric controls, arerelatively large and heavy, and are also expensive. Typically, a roomhaving an operating room-type table is set up in a medical facility, anda C-Arm is temporarily brought into the room when needed forfluoroscopic observations.

Due to increase in the number of outpatient centers and clinics,especially pain management clinics, a need has arisen for a low cost,transportable imaging stretcher. In pain management procedures, thepatient is placed on a support surface in a prone position and anerve-deadening solution is injected from a needle to precise areas ofthe spine. Fluoroscopy imaging with a C-Arm is used to determine thelocation of the needle in the patient during such procedures. The C-Armmust be positioned to visualize specific places on the spine whichrequires the C-Arm to be moved between the neck and the lower back of apatient resting on a support surface, tilted to odd angles, and rotatedfrom a vertical to a horizontal orientation without obstruction from thesurface supporting the patient. Caregivers will appreciate a low costimaging stretcher which includes an unobstructed X-ray window from thetailbone to the head of a patient resting on the support surface, withthe ability to angle and maneuver the C-Arm around and under thepatient.

There are some stretchers on the market today that have a radiolucenttop that can be used for C-Arm procedures, but have a relatively widesurface with metal structure down the sides that interfere with rotatingthe C-Arm and shooting an image horizontally or diagonally through apatient. Some of these stretchers have an upper deck or a litter thatslides end to end to achieve a large X-ray window, but they do not slidefar enough so that the C-Arm can position under the head of a patientsupported on the litter, and shoot an image diagonally through the neckwithout having to pull the C-Arm out from under the patient. Also inthese stretchers, the C-Arm cannot be moved from the head to the lowerback without obstruction. Some of these stretchers have a C-shaped basethat allows C-Arm access from one side only.

An imaging stretcher according to the present invention includes a basehaving a head end and a foot end, an upper deck formed from aradiolucent material, and actuators coupled to the base adjacent to thehead end and the foot end of the base respectively for movablysupporting the upper deck. According to one aspect of the invention, thehead end and foot end actuators are spaced wide apart to define acentral imaging region above the base which is free of any componentsthat would interfere with fluoroscopic imaging of a patient supported onthe upper deck.

According to another aspect of the invention,. the head end and foot endactuators are coupled to the upper deck such that the upper deck ismovable toward the foot end of the base. According to a further aspectof the invention, the upper deck may be unlocked, moved to a desiredposition and locked in place. According to still another aspect of theinvention, movement of the upper deck toward the foot end of the baselocates the head of a patient supported on the deck between the head endand foot end actuators in the central imaging region. According to afurther aspect of the invention, a portion of the base extending betweenthe head end and foot end actuators is formed to be closer to the floorthan the end sections thereof supporting the casters to provide moreclearance between the upper deck and the base between the actuators inthe central imaging region.

According to another aspect of the invention, the upper deck is movablebetween a lowered position and a raised position, and pivotable betweena first position where the foot end of the upper deck is raised abovethe head end thereof (also known as Trendelenberg position) and a secondposition where the head end of the upper deck is raised above the footend thereof (also known as reverse Trendelenberg position).

According to still further aspect of the invention, the upper deck isformed to include a cutout adjacent to the head end thereof to providespace for a patient's face lying in a prone position on the upper deck.According to another aspect of the invention, the upper deck is formedto include a pair of openings adjacent to first and second sides thereoffor supporting a pair of removable siderails. According to still anotheraspect of the invention, the upper deck is formed to include a pluralityof handles which are also made of radiolucent material. According to afurther aspect of the invention, the cutout, the openings for thesiderails and the handles are all integrally molded with the upper deck.

According to another aspect of the invention, an elongated shaft havinga longitudinal axis is coupled to the base for movement along thelongitudinal axis. A foot pedal is movably mounted to the base adjacentto the foot end, and is configured to engage a portion of the shaftadjacent to the foot end to move the shaft toward the head end and causethe head end actuator to adjust the elevation of the head end of theupper deck. According to yet another aspect of the invention, the shaftis mounted to the base for rotation about the longitudinal axis betweena first orientation and a second orientation. A steering wheel iscoupled to the shaft for movement relative to the base between a firstposition spaced apart from the floor when the shaft is rotated to thefirst orientation and a second position engaging the floor when theshaft is rotated to the second orientation.

Additional features of the present invention will become apparent tothose skilled in the art upon a consideration of the following detaileddescription of the preferred embodiments exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a side view of an imaging stretcher according to the presentinvention, showing a relatively narrow upper deck supported above arelatively low profile base by a pair of hydraulic cylinders which arespaced wide apart to form a central imaging region free of anynon-radiolucent components, the upper deck being mounted to the base formovement toward the foot end of the stretcher, and further showing inphantom the upper deck in a lowered position,

FIG. 2 is a side view similar to FIG. 1, showing the upper deck in aTrendelenberg position where a patient's feet are raised above the head,

FIG. 3 is a side view similar to FIGS. 1 and 2, showing the upper deckin a reverse Trendelenberg position where a patient's head is raisedabove the feet,

FIG. 4 is a plan view of the stretcher of FIGS. 1-3, showing the upperdeck formed to include a push handle near the head end, a pair ofdownwardly-sloping side handles near the foot end, a cutout near thehead end to provide space for a patient's face lying in a prone positionon the upper deck, a pair of armboards pivotally coupled near the headend of the upper deck for supporting a patient's arms, a pair ofopenings adjacent to the two sides of the upper deck for removablyreceiving a pair of siderails, and a cross bar near the head end of theupper deck for supporting one or more IV poles,

FIG. 5 is a plan view of the stretcher chassis without the upper deckand without a shroud covering the base, the base including two crossmembers held in longitudinally spaced apart relationship by twolongitudinally-extending, laterally-spaced siderails, a caster assemblycoupled to each end of the two cross members, a cross plate attached tothe two siderails at each end for supporting head end and foot endhydraulic pump/cylinder assemblies, a steering wheel support assemblymovably coupled to the two siderails intermediate of the two crossmembers, a longitudinally-extending, slidably-mounted brake-steer shaftcoupled to the steering wheel support assembly, a brake-steer butterflypedal pivotally mounted at each end of the two cross members, head endand foot end pressure release pedals movably coupled to the base nearthe foot end, a foot pump pedal mounted to the base near the foot endand coupled to hydraulic pumps for pumping fluid into the hydrauliccylinders,

FIG. 6 is a perspective view of the foot end of the base, showing thefoot end cross member, two longitudinally-extending siderails coupled tothe cross member, a caster assembly coupled to one end of the crossmember, a brake-steer butterfly pedal coupled to the brake-steer shaft,a pair of hydraulic pressure release pedals coupled to the foot end ofthe base, a linkage assembly coupling a head end pressure release pedalto the brake-steer shaft, and a foot pump pedal coupled to the base andcoupled to the hydraulic pumps,

FIG. 7 is a sectional view along the line 7—7 in FIG. 5, and showing thesteering wheel support assembly movably coupled to the siderails, anddisposed in a raised position spaced apart from the floor,

FIG. 8 is a sectional view similar to FIG. 7, and showing the steeringwheel support assembly in a lowered, floor-engaging position,

FIG. 9 is a perspective view showing a support assembly coupling thehead end of the upper deck to the head end hydraulic cylinder, the headend support assembly including two generally rectangular frames nestedwithin each other, the rectangular frames being pivotally coupled toeach other near their respective foot ends by a pair of pivot pins forrotation about a transversely-extending axis, and showing twolongitudinally-extending, laterally-spaced guide grooves formed on theunderside of the upper deck near the head end adjacent to the two sidesof the upper deck for receiving rim portions of a pair of wheelsrotatably mounted on said pivot pins, and further showing a pair ofrollers mounted to the underside of the upper deck near the head endadjacent to the two sides of the upper deck by a pair ofdownwardly-projecting brackets for reception in a pair ofoutwardly-opening channels formed in the outer rectangular frame,

FIG. 10 is a sectional view taken along the line 10—10 in FIG. 9 of thehead end of the upper deck, and showing the two generally rectangularnested frames, a roller coupled to the underside of the upper deck andreceived in an outwardly-opening channel formed in the outer rectangularframe, the head end hydraulic cylinder coupled to a cross member of theinner rectangular frame by a nut and bolt assembly,

FIG. 11 is a sectional view of a foot end of the upper deck taken alongthe line 11—11 in FIG. 4, a side handle with a portion broken away, afoot end cross member coupled to the foot end hydraulic cylinder by anut and bolt assembly, an upwardly-projecting bracket pivotally coupledto one end of the foot end cross member and supporting a pair ofrollers, the rollers being configured for reception in aninwardly-opening siderail coupled to the underside of the upper decknear the foot end adjacent to one side thereof for supportinglongitudinal movement of the upper deck within a given range, alongitudinally-extending locking rod attached to the underside of theupper deck near the foot end adjacent to said one side, a clampsupported by the foot end cross member and disposed about the lockingrod, the clamp normally securely gripping the locking rod to lock thesliding upper deck at a given longitudinal position, a release barpivotally mounted to the upper deck and coupled to the clamp for freeingthe upper deck when actuated to enable the caregiver to adjust thelongitudinal position of the upper deck,

FIG. 12 is a sectional view of the foot end of the upper deck takenalong the line 12—12 in FIG. 11, showing the side handle with portionsbroken away, two rollers in phantom received in the inwardly-openingsiderail coupled to the underside of the upper deck near the foot endadjacent to said one side, an upwardly-projecting bracket pivotallycoupled to the foot end cross member for supporting the rollers near thefoot end of the upper deck, the locking rod fixed to the underside ofthe upper deck, the clamp disposed about the locking rod, and a cablecoupling the release bar to the clamp,

FIG. 13 is a side view similar to FIG. 1, showing in dotted lines theupper deck slid toward the foot end of the stretcher, and furthershowing in solid lines the C-Arm positioned adjacent to the head of apatient supported on the upper deck and tilted about atransversely-extending axis to shoot an image diagonally through theneck, and further showing in phantom lines the C-Arm positioned adjacentto the lower back of the patient and tilted to shoot an image diagonallythrough the tailbone,

FIG. 14 is an end view of the stretcher, showing the C-Arm rotated abouta longitudinally-extending axis to shoot an image through the head of apatient supported on the upper deck without interference from siderailsor any other metal structures in the imaging region, and

FIG. 15 is a plan view similar to FIG. 4, showing the upper deck formedto include a cutout near the head end to provide space for a patient'sface lying in a prone position on the upper deck.

DETAILED DESCRIPTION OF THE DRAWINGS

Although the term “stretcher” is used throughout the specification, itis understood that the novel features of the invention may beincorporated into any type of a patient support device—such as ahospital bed or an operating table. Also, although the term“fluoroscopy” is used throughout the specification for convenience, itwill be construed to include any other type of imaging. Also the terms“hydraulic pump” or “hydraulic cylinder” or “hydraulic pump/cylinderassembly” will be construed to include any hydraulic, pneumatic,mechanical or electrical device for lifting, lowering or tilting theupper deck. In other words, the features of the present invention arenot to be limited to the use with a stretcher or a fluoroscope or ahydraulic device.

Referring to FIGS. 1-4, a stretcher 20 in accordance with the presentinvention includes a low profile base 22 with a relatively largewheelbase, a relatively narrow slidably-mounted upper deck 24 coupled tothe base 22, a protective shroud 26 covering the base 22, a head end 32,a foot end 34, an elongated first side 36, an elongated second side 38and a longitudinal axis 40. As used in this description, the phrase“head end 32” will be used to denote the end of any referred-to objectthat is positioned to lie nearest the head end 32 of the stretcher 20,and the phrase “foot end 34” will be used to denote the end of anyreferred-to object that is positioned to lie nearest the foot end 34 ofthe stretcher 20. Likewise, the phrase “first side 36” will be used todenote the side of any referred-to object that is positioned to lienearest the first side 36 of the stretcher 20 and the phrase “secondside 38” will be used to denote the side of any referred-to object thatis positioned to lie nearest the second side 38 of the stretcher 20.

The upper deck 24 is formed from a radiolucent material—end to end andside to side—to facilitate fluoroscopic observations of a patientsupported on the upper deck 24—for example, for conducting painmanagement procedures. The stretcher 20 is particularly suitable for usein endoscopy, cardiac catheterization, and other procedures requiringfluoroscopy. As shown in FIG. 13, the deck 24 is movable toward the footend 34 of the stretcher 20 so that a C-Arm 42 can position under thehead of a patient supported on the upper deck 24 and tilted about atransversely-extending axis to shoot an image diagonally through theneck of the patient without pulling the C-Arm out from under thepatient. Relatively narrow upper deck 24 (about 20 inches or 50centimeters wide) allows the C-Arm 42 to rotate about alongitudinally-extending axis from a vertical orientation to ahorizontal orientation, as shown in FIG. 14, to shoot an imagehorizontally through the head of a patient supported on the upper deck24 without interference from siderails—particularly non-removable metalsiderails.

The base 22 is supported on floor 28 by four caster assembles 30 toallow the stretcher 20 to be rolled over the floor 28 to transport apatient. The upper deck 24 is movably supported above the base 22 by alifting mechanism 50 in order to raise, lower, and tilt the upper deck24 relative to the base 22. Illustratively, the upper deck liftingmechanism 50 includes head end and foot end hydraulic cylinders 52 and54 covered by flexible boots 56. The hydraulic cylinders 52, 54(sometimes referred to herein as the actuators) are spaced wide apart(about 60 inches or 150 centimeters) to provide room for maneuvering theC-Arm 42. The hydraulic cylinders 52, 54 are coupled to respectivehydraulic pumps 62 and 64 supported on the base 22. The head endhydraulic cylinder 52 controls the vertical position of the head end 32of the upper deck 24 relative to the base 22, and the foot end hydrauliccylinder 54 controls the vertical position of the foot end 34 of theupper deck 24 relative to the base 22. The hydraulic cylinders 52, 54adjust the vertical position of the upper deck 24 between a low position(about 24 inches or 60 centimeters above the floor) to facilitatepatient egress and ingress, and a high position (about 40 inches or 102centimeters above the floor) to provide a comfortable position for aSurgeon standing next to a patient supported on the upper deck 24. Inaddition, the hydraulic cylinders 50, 52 tilt the upper deck 24 to oneof three positions—a flat, horizontal position shown in FIG. 1, aTrendelenburg position shown in FIG. 2 where a patient's feet are raisedabove the patient's head, or a reverse Trendelenburg position shown inFIG. 3 where the patient's head is raised above the patient's feet.

A mattress pad 70 may be disposed on the upper deck 24 for supporting apatient as shown in FIGS. 1 and 14. The mattress pad 70 may includeselectively activated, inflatable bladders to provide special supportthat may be required for certain medical procedures—such as imaging apatient's spine when the patient is lying in a prone position on thedeck 24, for example, for pain management procedures. The upper deck 24is configured to form a raised, gently-curved push handle 72 near thehead end 32 of the stretcher 20, and two downwardly-sloping side handles74 near the foot end 34 adjacent to the two sides 34, 36 of thestretcher 20 as shown in FIGS. 1-4. A caregiver can grip either the headend push handle 72 or the two foot end side handles 74 to maneuver thestretcher 20 over the floor 20. After unlocking the upper deck 24, thecaregiver may use the head end push handle 72 or the foot end sidehandles 74 to move the upper deck 24 to a desired position, and thenlock the upper deck 24 in place. As indicated, the caregiver may wish tomove the upper deck 24 to a different position to view a differentportion of a patient's body for a diagnostic or a surgical procedure.The ergonomic designs of the handles 72, 74 provide a comfortable grip.

As shown in FIGS. 4 and 15, a cutout 76 is formed in the upper deck 24to provide space for a patient's face lying in a prone position on theupper deck 24. In accordance with one aspect of the present invention,the stretcher 20 is configured such that the cutout 76 is locatedbetween the hydraulic cylinders 52, 54 in an X-ray window 300 when thedeck 24 is moved toward the foot end 34 of the stretcher 20 tofacilitate shooting an image diagonally through the neck of the patientas shown in FIG. 13. A transversely-extending cross bar 84 is secured tothe upper deck 24 near the head end 32 of the stretcher 20. Inaccordance with another aspect of the present invention, an armboard 78is pivotally coupled to each end of the cross bar 84 by a pivot pin 78′adjacent to the two sides 34, 36 for movement between a first positionextending toward the foot end and a second position extending away fromthe foot end for supporting a patient's arms. Pivoting armboards 78allow prone patients to position their arms over their heads and stillbe supported by the armboards 78 as shown in FIG. 4. The upper deck 24is further configured to form openings 80 adjacent to the two sides 34,36 for removably receiving a pair of plug-in siderails 82 as shown inFIG. 1. The removable siderails 82 allow shooting an image diagonallythrough the head or the tailbone of a patient supported on the upperdeck 24 without interference from the siderails 82 as shown in FIG. 14.One or more IV poles may be secured to the cross bar 84 near the headend 32 of the stretcher 20 for holding solution containers or otherobjects at a position elevated above the upper deck 24. The foot endportion 88 of the upper deck 24 may be angled away from the upper deck24 to provide comfortable ankle support for a patient lying in a proneposition on the upper deck 24. Illustratively, the upper deck 24 ismolded from a radiolucent foam plastic material and provided with fiberglass outer shell. The handles 72, 74, the cutout 76 and the siderailopenings 80 may all be integrally molded with the upper deck 24.

The combination of a relatively narrow deck (about 20 inches or 50centimeters), a high position of the deck 24 when raised to a fullheight (about 40 inches or 102 centimeters above the floor) and widelyspaced-apart hydraulic cylinders 52, 54 (about 60 inches or 150centimeters) can cause instability. Stability is very important duringthese types of procedures, and the litter 24 must not wobble. Also, thelitter 24 must be stable for a patient to get on and off. Typically, ORtables (Operating Room tables) have a very heavy base to add stability.A heavy base is not acceptable on fluoroscopic-type stretchers that havesome intention of being transportable. A wide wheelbase (about 24 inchesor 60 centimeters) is therefore desired for stability along with anarrow top (about 20 inches or 50 centimeters) to allow rotation of theC-arm 42 about a longitudinally-extending axis as shown in FIG. 14.However, the caster assemblies 30 or the brake-steer pedals 114 cannotprotrude farther out than the upper deck 24 as it creates a trip hazardif walking around the stretcher 20. In accordance with an aspect of thepresent invention, the side handles 74 and the armboards 78 extendoutwardly from the deck 24 beyond the caster assemblies 30 and thebrake-steer pedals 114 coupled to the base 22. Thus, the casterassemblies 30 and the brake-steer pedals 114 remain within the footprintof the upper deck 24, the side handles 74 and the armboards 78.

As shown in FIG. 5, the base 22 includes a head end cross member 92 anda foot end cross member 94. The head end and foot end cross members 92,94 are held in longitudinally spaced apart relationship by twolongitudinally-extending, laterally-spaced siderails 96 and 98 securedto downwardly-extending brackets (not shown) fixed to the cross members92, 94. The two longitudinally-extending siderails 96, 98 have step-downmiddle portions 100 that are configured to be closer to the floor 28(about 4 inches or 10 centimeters from the floor 28) than theirrespective end portions (about 13 inches or 33 centimeters from thefloor 28). The step-down middle portions 100 of the base 22 providesmore vertical clearance between the base 22 and the upper deck 24between the two hydraulic cylinders 52, 54 in the central imaging region300 for the C-Arm 42. High end portions of the base 22, on the otherhand, allow use of larger caster assemblies 30. A short end section 102is attached at each end of the two siderails 96, 98 to lend rigidity tothe structure. Coupled to each end of the two cross members 92, 94 is anoutwardly-extending right angle bracket 104. Each right angle bracket104 supports a caster assembly 30 and a brake-steer butterfly pedal 114.A cross plate 106 is attached to the two siderails 96, 98 near the headend 32 of the base 22 to support the head end hydraulic cylinder/pumpassembly 52/62. Likewise, another cross plate 106 is attached to the twosiderails 96, 98 near the foot end 34 of the base 22 to support the footend hydraulic cylinder/pump assembly 54/64. The cross members 92, 94,the siderails 96, 98 and short end sections 102 are in the form ofextruded tubes having a square cross section, and made from rigid highstrength, light weight materials—such as steel or aluminum.

A longitudinally-extending brake-steer shaft 108 is slidably androtatably mounted to the siderail 98 near the second side 38 of the base22 by a plurality of brackets 110 as shown in FIG. 5. The brake-steershaft 108 rotates about its longitudinal axis 112 in either direction inresponse to rotation of a brake-steer butterfly pedal 114, and istranslatable in a longitudinal direction, indicated by a double-headedarrow 116, either toward or away from the foot end 34 in response to theoperation of a head end pressure release pedal 182 coupled to the footend 34 of the base 22. A linkage assembly 122 couples the brake-steershaft 108 to two brake-steer pedals 114 at the head end 32 of thestretcher 20. Likewise, a linkage assembly 124 couples the brake-steershaft 108 to two brake-steer pedals 114 at the foot end 34 of thestretcher 20. Since the two linkage assemblies 122, 124 are similar toeach other, only the foot end linkage assembly 124 will be described.

Referring to FIG. 6, the foot end linkage assembly 124 includes a crossshaft 126 having its ends rotatably supported by two outwardly-extendingright angle brackets 104 coupled to the foot end cross member 94.Another bracket 128, having a C-configuration in plan view, supports thecross shaft 126 intermediate of the two right angle brackets 104. Thebracket 128 includes two vertically-disposed side plates 128′ held inlaterally spaced apart relation by a crosswise back plate 128″. The backplate 128″ is fixed to the foot end cross member 94. A brake-steer pedal114 is fixed to each end of the cross shaft 126. A bent link 130 has afirst end 130′ fixed to the cross shaft 126 between the twovertically-extending side plates 128′ of the bracket 128, and a secondend 130″ pivotally coupled to a first end 132′ of a connecting link 132.The second end 132″ of the connecting link 132 is pivotally coupled to afirst end 134′ of a short link 134. A second end 134″ of the short link134 is fixed to the foot end 34 of the brake-steer shaft 108.

The brake-steer pedal 114 has three positions—(a) a generally horizontalneutral position, (aa) a braking position where a braking portion 136 ofthe brake-steer pedal 114 is angled downwardly and an opposite steeringportion 138 of the brake-steer pedal 114 is angled upwardly, and (aaa) asteering position where the steering portion 138 of the brake-steerpedal 114 is angled downwardly and the braking portion 136 of thebrake-steer pedal 114 is angled upwardly. When the brake-steer pedal 114is generally horizontal, the caster assemblies 30 are free to swivel androtate. From the generally horizontal neutral position, the caregivercan depress the braking portion 136 of the brake-steer pedal 114 in ananticlockwise braking direction indicated by arrow 140 in FIG. 6 to abraking position. Rotation of the brake-steer pedal 114 to the brakingposition moves brake shoes (not shown) into engagement with the casterassemblies 30 to lock the caster assemblies 30 in place.

From the braking position, the caregiver can depress the steeringportion 138 of the brake-steer pedal 114 to rotate the brake-steer pedal114 back to the horizontal neutral position. When the brake-steer pedal114 is in the neutral position, the caregiver can depress the steeringportion 138 of the brake-steer pedal 114 to rotate the cross shaft 126in a clockwise steering direction indicated by arrow 142 in FIG. 6 to asteering position. Rotation of the cross shaft 126 to the steeringposition, causes the bent link 130 to also rotate in the clockwisedirection 142 to, in turn, cause the connecting link 132 to move in adownwardly direction indicated by arrow 144 and cause the short link 134and the brake-steer shaft 108 to rotate in an anticlockwise directionindicated by arrow 146 in FIG. 6. Rotation of the brake-steer shaft 108in the anticlockwise direction 146 causes a steering wheel supportassembly 150 to lower a pair of steering wheels 152 to engage the floor28.

As shown in FIGS. 5, 7 and 8, the steering wheel support assembly 150includes a shaft 154 having the wheels 152 (also referred to herein ascenter or steering wheels) mounted side-by-side thereon. The shaft 154is fixed to the foot end 34 of an elongated wheel-mounting bracket 156.The head end 32 of the wheel-mounting bracket 156 is pivotally coupledto a cross plate 158 having its ends attached to the siderails 96, 98.The wheel-mounting bracket 156 is movable between a raised positionshown in FIG. 7 where the steering wheels 152 are spaced apart from thefloor 28, and a lowered position shown in FIG. 8 where the steeringwheels 152 are in engagement with the floor 28. A vertically-extendingspring 160 extends between the foot end 34 of the wheel-mounting bracket156 and the siderail 96. The vertically-extending spring 160 normallybiases the wheel-mounting bracket 156 to the raised position spacedapart from the floor 28. Fixed to the wheel-mounting bracket 156 is atransversely-extending cam plate 162 having a downwardly sloping endportion 164 extending toward the brake-steer shaft 108. The downwardlysloping end portion 164 of the cam plate 162 is configured forengagement with a cam 166 mounted on the brake-steer shaft 108. Asexplained above, rotation of the steer portion 138 of the brake-steerpedal 114 in the clockwise direction 142 to the steering position causesthe brake-steer shaft 108 to rotate in the anticlockwise direction 146shown in FIG. 6. Rotation of the brake-steer shaft 108 in theanticlockwise direction 146 causes the cam 166 fixed thereto to alsorotate in an anticlockwise direction indicated by arrow 168 in FIG. 7.Rotation of the cam 164 to in the anticlockwise direction 168 displacesthe wheel-mounting bracket 156 in a downward direction indicated byarrow 170, causing the steering wheels 152 to engage the floor 28 asshown in FIG. 8.

The upper deck lifting mechanism 50 includes a foot pump pedal 180, ahead end pressure release pedal 182 and a foot end pressure releasepedal 184 as shown in FIG. 6. The pedals 180-184 are pivotally coupledto the base 22 near the foot end 34 of the stretcher 20, and control thevertical movement of the head end 32 and the foot end 34 of the upperdeck 24. From their generally horizontal operative positions shown inFIG. 6, the pressure release pedals 182, 184 can be flipped up to theirrespective, generally vertical out-of-the-way inoperative positions.

Referring to FIGS. 1-3, 5 and 6, an actuating member 186 includes anoutwardly-extending, generally horizontal portion 188, an intermediatebase portion 190 and a downwardly-extending, generally vertical portion192. The foot pump pedal 180 is fixed to the free end of the generallyhorizontal, outwardly-extending portion 188. As shown in FIG. 5, thebase portion 190 of the actuating member 186 is attached to a crossshaft 194 rotatably coupled to the siderails 96, 98 near the foot end 34of the stretcher 20. As shown in FIGS. 1-3, the free end of thegenerally vertical portion 192 of the actuating member 186 is coupled tothe foot end 34 of a longitudinally-extending, reciprocally-mountedshaft 198 through a right angle member 196 such that verticalreciprocating motion of the foot pump pedal 180 causes horizontalreciprocating motion of the shaft 198. The longitudinally-extendingshaft 198 is slidably mounted to the siderail 96 near the first side 36of the stretcher 20 (on the side opposite from thelongitudinally-extending brake-steer shaft 108) by a plurality ofbrackets 200 for movement toward and away from the foot end 34 of thestretcher 20 in a direction indicated by a double-headed arrow 202 inFIG. 5. The longitudinally-extending shaft 198 is coupled to the headend hydraulic pump 62 near the head end 32 of the stretcher 20 (FIGS.1-3), and to the foot end hydraulic pump 64 near the foot end 34 of thestretcher 20. As shown in FIGS. 1-3 and 6, a generallyhorizontally-extending spring 204 is coupled between the free end of thegenerally vertical portion 192 and the foot end 34 of the siderail 96 tobias the foot pump pedal 180 upwardly to a generally-horizontal raisedposition shown in FIG. 6. From the generally-horizontal raised position,the caregiver can depress the foot pump pedal 180 to cause thelongitudinally-extending shaft 198 to move toward the foot end 34 of thestretcher 20. Caregiver can then release the pressure on the foot pumppedal 180 to allow the generally horizontally-extending spring 204 topull the longitudinally-extending shaft 198 away from the foot end 34 ofthe stretcher 20, and to lift the foot pump pedal 180 upwardly to thegenerally-horizontal raised position shown in FIG. 6. Caregiver can thenagain depress the foot pump pedal 180. Reciprocating motion of the shaft198 causes the pumps 62, 64 to pump fluid into the hydraulic cylinders52, 54 respectively to, in turn, cause the upper deck 24 to rise.

As shown in FIG. 6, an actuating member 210 includes anoutwardly-extending, generally horizontal portion 212, an intermediatebase portion 214 and a downwardly-extending, generally vertical portion216. The head end pressure release pedal 182 is coupled to the free endof the generally horizontal portion 212. The base portion 214 of theactuating member 210 is pivotally coupled to a c-shaped bracket 218mounted to the foot end 34 of the siderail 98 near the second side 38 ofthe stretcher 20. The free end of the downwardly-extending portion 216is configured to engage a transverse plate 220 fixed on the brake-steershaft 108 near the foot end 34 thereof From a generally horizontalposition shown in FIG. 6, the caregiver can depress the head endpressure release pedal 182 to thereby cause the downwardly-extendingportion 216 of the actuating member 210 to rotate in a clockwisedirection indicated by arrow 222. Rotation of the generally verticalportion 216 in the clockwise direction 222 pushes the transverse plate220 and the brake-steer shaft 108 coupled thereto toward the head end 32of the stretcher 20. When the brake-steer shaft 108 moves toward thehead end 32, a transversely-mounted actuator 224 coupled to thebrake-steer shaft 108 depresses a pressure release pin or button 226coupled to the head end hydraulic pump 62 as shown in FIG. 5 to releasethe pressure in the head end hydraulic cylinder 52 to, in turn, lowerthe head end 32 of the upper deck 24. As shown in FIG. 5, a generallyhorizontally-extending spring 228 coupled between the brake-steer shaft108 and the siderail 98 biases the brake-steer shaft 108 to return toits original position when the pressure release pedal 182 is freed.

An actuating member 240 includes an outwardly-extending, generallyhorizontal portion 242, an intermediate base portion and adownwardly-extending, generally vertical portion. The foot end pressurerelease pedal 184 is coupled to the free end of the generally horizontalportion 242. The base portion of the actuating member 240 is pivotallycoupled to a c-shaped bracket 248 mounted to the foot end 34 of thesiderail 98 near the second side 38 of the stretcher 20. When the footend pressure release pedal 1 84 is depressed, the free end of thedownwardly-extending portion depresses a pressure release pin or buttoncoupled to the foot end hydraulic pump 64 to release the pressure in thefoot end hydraulic cylinder 54 to, in turn, lower the foot end 34 of theupper deck 24.

Referring to FIGS. 9-12, the head end 32 of the radiolucent upper deck24 is coupled to the head end hydraulic cylinder 52 by a head endsupport assembly 302, and the foot end 34 of the deck 24 is coupled tothe foot end hydraulic cylinder 54 by a foot end support assembly 304.As previously explained, the head end cylinder 52 controls a verticalposition of the head end 32 of the upper deck 24, and the foot endcylinder 54 controls a vertical position of the foot end 34 of the upperdeck 24. As shown in FIGS. 1-3, the head end and foot end supportassemblies 302, 304 are spaced wide apart (about 60 inches or 150centimeters) to define the central imaging region 300 above the base 22between the head end and foot end hydraulic cylinders 52, 54 which isfree of any metallic structures that would interfere with imaging. Thetwo support assemblies 302, 304 (sometimes referred to herein as thehead end and foot end connectors) secure the upper deck 24 to the base22, while allowing translation of the upper deck 24 toward the foot end34 of the stretcher 20 so that a C-Arm 42 can be positioned anyplacefrom the neck to the tailbone of a patient supported on the deck 24 ortilted to a suitable angle as shown in FIG. 13, or rotated from avertical to a horizontal orientation as shown in FIG. 14 without anyobstruction and without having to pull the C-Arm out from under thepatient. For example, the C-Arm 42 can be located near the head end 32of the stretcher 20 and tilted as shown in FIG. 13 to shoot an imagediagonally through the neck of the patient.

As shown in FIGS. 9 and 10, the head end support assembly 302 includes agenerally rectangular inner frame 312 nested inside a generallyrectangular outer frame 314. The inner and outer frames 312, 314 arepivotally coupled to each other near their respective foot ends 34 forrotation about a first transversely-extending axis 316. The inner frame312 includes first and second longitudinally-extending siderails 322,324 in the form of inwardly-opening channels. Thelongitudinally-extending siderails 322, 324 are held in laterally spacedapart relationship by a head end cross member 332 in the form of acircular tube and a foot end cross member 334 in the form of a squaretube. The head end cross member 332 is rigidly attached to the head endhydraulic cylinder 52 by a nut and bolt assembly 336. The outer frame314, on the other hand, includes first and secondlongitudinally-extending siderails 342, 344 in the form ofoutwardly-opening channels. The longitudinally-extending siderails 342and 344 are held in laterally spaced apart relationship by a head endcross member 352 in the form of a square tube and a foot end crossmember 354 in the form of a rectangular plate mounted on the top side ofthe outer frame 314. The foot ends 34 of the inner siderails 322, 324and. the foot ends 34 of the outer siderails 342, 344 are pivotallycoupled to each other by pivot pins 358 for rotation about thetransversely-extending axis 316. Pivotal coupling of the inner and outerframes 312, 314 allows the upper deck 24 to pivot to a Trendelenburgposition shown in FIG. 2 or to a reverse Trendelenburg position shown inFIG. 3.

The underside of the upper deck 24 is formed to include twolongitudinally-extending, laterally-spaced guide grooves 362 forreceiving rim portions of wheels 372 freely rotatable on the pivot pins358. The wheels 372 are located between the outer walls of the innersiderails 322, 324 and the inner walls of the outer siderails 342, 344adjacent to the foot ends 34 of the inner and outer frames 312, 314. Theoutwardly-opening channels 342, 344 of the outer frame 314 areconfigured to receive a pair of rollers 382 mounted to the underside ofthe upper deck 24 for rotation about a second transversely-extendingaxis 386 by a pair of downwardly-projecting brackets 392. As shown inFIG. 10, a pair of guard members 402 in the form of inwardly-openingchannels are coupled to the outwardly-opening channels 342, 344 by platemembers 412 mounted on the bottom side thereof to form enclosed tracks416 for receiving the rollers 382 mounted to the underside of the upperdeck 24. The outwardly-facing top edges 418 of the outer channel members342, 344 and the inwardly-facing top edges 420 of the guard members 402form longitudinally-extending channels or slots 422 along the two sidesof the upper deck 24 for slidably receiving the roller-supportingbrackets 392. The reception of the rollers 382 mounted to the undersideof the upper deck 24 in the enclosed tracks 416 secures the head end 32of the upper deck 24 to the base 22, while allowing the upper deck 24 totranslate longitudinally relative to the base 22 within a certainlimited range.

Referring to FIGS. 11 and 12, the foot end support assembly 304 includesa cross member 424 in the form of a circular tube rigidly attached tothe foot end hydraulic cylinder 54 by a nut and bolt assembly 426. Anupwardly-projecting bracket 432 is pivotally attached to the each end ofthe tubular cross member 424 for rotation about a thirdtransversely-extending axis 436. Pivotal movement of the brackets 432relative to the foot end cross member 424 allows the upper deck 24 topivot to a Trendelenburg position shown in FIG. 2 or to a reverseTrendelenburg position shown in FIG. 3. Each of the brackets 432supports a pair of rollers 442 configured for reception in the first andsecond longitudinally-extending, inwardly-opening channels 452 mountedto the underside of the upper deck 24 adjacent to the foot end 34thereof Reception of the rollers 442 mounted to the cross member 424 inthe inwardly opening channels 452 mounted to the underside of the upperdeck 24 holds the foot end 34 of the upper deck 24 in place, whileallowing the upper deck 24 to translate longitudinally within apredetermined range relative to the base 22.

When the upper deck 24 is horizontal as shown in FIG. 1, a patient'sweight is transferred to the rollers 382 near the head end 32 of thestretcher 20, and to the rollers 442 near the foot end 34 of thestretcher 20. The patient's weight on the rollers 382 near the head end32 of the stretcher 20 is transferred to the outer siderails 342, 344(urging the outer siderails 342, 344 to rotate about thetransversely-extending axis 316 in a clockwise direction 456 shown inFIG. 9), then to the inner frame 312 through the top cross plate 354,and finally to the head end hydraulic cylinder 52 through the head endcross member 332. On the other hand, the patient's weight on the rollers442 near the foot end 34 of the stretcher 20 is transferred to the footend cross member 424 through the pivotally-mounted brackets 432, andthen to the foot end hydraulic cylinder 54 through the foot end crossmember 424.

To move the upper deck 24 to the Trendelenburg position shown in FIG. 2from the horizontal position shown in FIG. 1, hydraulic pressure in thehead end hydraulic cylinder 52 is released by using the head endpressure release pedal 182 coupled to the foot end 34 of the stretcher20, causing the head end cross member 332 to move down. When the headend cross member 332 moves down, both the inner and outer frames 312 and314 move down, and the upper deck 24 pivots about the axis 386 of therollers 382 near the head end 32 of the stretcher 20 and the axis 436 ofthe pivotally-mounted brackets 432 near the foot end 34 of the stretcher20. In the Trendelenburg position, a patient's weight is transferred tothe rollers 382 near the head end 32 of the stretcher 20, and to therollers 442 near the foot end 34 of the stretcher 20. The patient'sweight on the rollers 382 near the head end 32 of the stretcher 20 istransferred to the outer siderails 342 (urging the outer siderails 342,344 to rotate about the transversely-extending axis 316 in a clockwisedirection 458 in FIG. 2), then to the inner frame 312 through the topcross plate 354, and finally to the head end hydraulic cylinder 52through the head end cross member 332. On the other hand, the patient'sweight on the rollers 442 near the foot end 34 of the stretcher 20 istransferred to the foot end cross member 424 through thepivotally-mounted brackets 432, and to the foot end hydraulic cylinder54 through the foot end cross member 424.

To move the upper deck 24 to the reverse Trendelenburg position shown inFIG. 3 from the horizontal position shown in FIG. 1, hydraulic pressurein the foot end hydraulic cylinder 54 is released by using the foot endpressure release pedal 184 coupled to the foot end 34 of the stretcher20 to cause the foot end cross member 424 to move down. When the footend cross member 422 moves down, the outer frame 314 pivots about theaxis 316 of the wheels 372 near the head end 32 of the stretcher 20 inthe direction 460 in FIG. 3. The upper deck 24, on the other hand,pivots about the axis 316 of the wheels 72 near the head end 32 of thestretcher 20, and about the axis 436 of the pivotally-mounted brackets432 near the foot end 34 of the stretcher 20. In the reverseTrendelenburg position, a patient's weight is transferred to the wheels372 near the head end 32 of the stretcher 20, and to the rollers 442near the foot end 34 of the stretcher 20. The patient's weight on thewheels 372 near the head end 32 of the stretcher 20 is transferred tothe inner frame 312 through the pivot pins 358, and then to the head endhydraulic cylinder 52 through the head end cross member 332. On theother hand, the patient's weight on the rollers 442 near the foot end 34of the stretcher 20 is transferred to the foot end cross member 424through the pivotally-mounted brackets 432, and then to the foot endhydraulic cylinder 54 through the foot end cross member 424.

Thus, the novel configuration of the head end and foot end supportassemblies 302 and 304 allows the upper deck 24 to move toward the footend 34 of the stretcher 20, so that a C-Arm 42 can be positionedanyplace from the neck to the tailbone of a patient supported on thedeck 24, or tilted about a tranversely-extending axis as shown in FIG.13, or rotated about a longitudinally-extending axis as shown in FIG. 14without any obstruction and without the necessity of pulling the C-Armout from under the patient. The support assemblies 302, 304 also allowthe entire upper deck 24 to be raised or lowered as shown in FIG. 1,move the upper deck 24 to a Trendelenburg position as shown in FIG. 2 orto a reverse Trendelenburg position as shown in FIG. 3.

An upper deck locking mechanism 470 is provided for selectively lockingthe upper deck 24 at a given longitudinal position with respect to thebase 22 as shown in FIGS. 11 and 12. The upper deck locking mechanism470 includes a longitudinally-extending locking rod 472 attached to theunderside of the foot end 34 of the upper deck 24 near the first side 36of the stretcher 20 by means of a pair of downwardly projecting brackets474. A clamp 476 is disposed about the rod 472, and is secured to thefoot end cross member 424 by a bracket 478. The clamp 476 is normallybiased to tightly grip the rod 472 to lock the upper deck 24 in place. Aupper deck release bar 480 is pivotally mounted to the siderail 452adjacent to the foot end side handle 64 near the first side 36 of thestretcher 20. The release bar 480 is normally biased in a direction awayfrom the side handle 64. A cable 482 has one end 484 secured to therelease bar 480 and a second end 486 secured to the clamp 476. To freethe upper deck 60, the release bar 480 is lifted toward the side handle64. When the release bar 480 is lifted, the end 484 of the cable 482attached to the release bar 480 is pulled. When the end 484 of the cable482 is pulled, the second end 486 of the cable 482 secured to the clamp476 pulls on the clamp 476 to open it up to release the locking rod 472to, in turn, free the upper deck 24 to move longitudinally relative tothe base 22.

Although the invention has been described in detail with reference to acertain preferred embodiment, variations and modifications exist withinthe scope and spirit of the invention as described and as defined in thefollowing claims.

What is claimed is:
 1. A patient support apparatus comprising: anelongated base having first and second ends, a plurality of castersrotatably mounted to the base, and engaging a floor, an upper deck,first and second actuators coupled to the base adjacent to the first andsecond ends thereof respectively for movably supporting the upper deckbetween a low position and a high position, the first actuatorcontrolling a vertical position of a first end of the upper deck and thesecond actuator controlling a vertical position of a second end of theupper deck, an elongated shaft having a longitudinal axis, the shaftbeing coupled to the base for rotation about the longitudinal axisbetween a first orientation and a second orientation, and for movementalong the longitudinal axis, a wheel coupled to the shaft for movementrelative to the base between a first position spaced apart from thefloor when the shaft is rotated to the first orientation, and a secondposition engaging the floor when the shaft is rotated to the secondorientation, and a foot pedal movably mounted to the base adjacent tothe second end thereof, the foot pedal being configured to engage aportion of the shaft adjacent to the second end of the base to move theshaft toward the first end and cause the first actuator to adjust thevertical position of the first end of the upper deck.
 2. The apparatusof claim 1, wherein the first and second ends of the base correspond toa head end and a foot end thereof, wherein the first and secondactuators correspond to a head end actuator and a foot end actuator, andwherein the foot pedal is movably mounted to the base adjacent to thefoot end thereof, and is configured to engage said portion of the shaftadjacent to the foot end to move the shaft toward the head end and causethe head end actuator to lower the head end of the upper deck.
 3. Theapparatus of claim 2, wherein actuators are hydraulic cylinders, whereinthe apparatus further includes a foot pump pedal movably mounted to thebase adjacent to the foot end thereof, and coupled to the hydrauliccylinders for pumping fluid into the respective hydraulic cylinders forraising the upper deck relative to the base.
 4. The apparatus of claim3, wherein the head end hydraulic cylinder includes a pressure releasebutton, and wherein a portion of the shaft adjacent to the head end ofthe base is configured to engage said pressure release button when theshaft is moved toward the head end, and release hydraulic pressure inthe head end hydraulic cylinder to lower the head end of the upper deck.5. The apparatus of claim 4, further including a first linkage assemblyfor selectively coupling the foot pedal to said portion of the shaftadjacent to the foot end.
 6. The apparatus of claim 5, wherein the firstlinkage assembly includes an actuating member having anoutwardly-extending, generally horizontal portion, an intermediate baseportion and a downwardly-extending, generally vertical portion, whereinthe foot pedal is coupled to the free end of the generally horizontalportion, wherein the base portion of the actuating member is pivotallycoupled to the foot end of the base, wherein actuation of the foot pedalcauses rotation of the downwardly-extending portion of the actuatingmember, wherein the free end of the downwardly-extending portion isconfigured to engage said portion of the shaft near the foot end thereofand cause translation of the shaft toward the head end, and whereintranslation of the shaft toward the head end causes actuation of thepressure release button to release the pressure in the head endhydraulic cylinder to, in turn, lower the head end of the upper deck. 7.The apparatus of claim 5, wherein the first linkage assembly furtherincludes a transverse plate attached to the shaft adjacent to the footend, wherein the free end of the downwardly-extending portion isconfigured to engage said transverse plate and cause translation of thetransverse plate and the shaft attached thereto toward the head end, andwherein translation of the shaft toward the head end causes actuation ofthe pressure release button to release the pressure in the head endhydraulic cylinder to, in turn, lower the head end of the upper deck. 8.The apparatus of claim 7, wherein the first linkage assembly furtherincludes a spring coupled to the shaft to bias the shaft to return toits original position when the foot pedal is released.
 9. The apparatusof claim 4, further including a second foot pedal movably mounted to thebase adjacent to the foot end thereof, wherein the foot end hydrauliccylinder includes a pressure release button, wherein the second footpedal is configured to engage the pressure release button coupled to thefoot end hydraulic cylinder and release hydraulic pressure in the footend hydraulic cylinder to lower the foot end of the upper deck.
 10. Theapparatus of claim 1, further including a brake-steer pedal mounted tothe base near the foot end thereof for movement between a brake positionand a steer position, and a foot end linkage assembly for coupling thebrake-steer pedal to the shaft such that the shaft is moved to the firstorientation and the wheel is spaced apart from the floor when thebrake-steer pedal is moved to the brake position, and the shaft is movedto the second orientation and the wheel is engaging the floor when thebrake-steer pedal is moved to the steer position.
 11. The apparatus ofclaim 10, wherein the shaft has a third neutral position intermediate ofthe brake and steer positions thereof.
 12. The apparatus of claim 10,wherein the foot end linkage assembly includes a cross shaft rotatablycoupled to the foot end of the base, the cross shaft supporting abrake-steer pedal adjacent to each end thereof, the foot end linkageassembly further including a bent link fixed to the cross shaft, aconnecting link having one end pivotally coupled to the bent link and asecond end pivotally coupled to a short link fixed to the foot end ofthe shaft, wherein rotation of the brake-steer pedal to the brakeposition causes the shaft to rotate to the first orientation and liftthe wheel off the floor, and wherein rotation of the brake-steer pedalto the steer position causes the shaft to rotate to the secondorientation and lower the wheel to engage the floor.
 13. The apparatusof claim 1, further including a steering wheel support assembly tocouple the shaft to the wheel, wherein the steering wheel supportassembly includes a bracket supporting the wheel and pivotally coupledto the base for movement between a first position where the wheel isspaced apart from the floor and a second position where the wheel isengaging the floor, a spring biasing the bracket to the first positionwhere the wheel is spaced apart from the floor, and a cam fixed to theshaft and configured to engage the bracket to cause movement of thebracket to the second position where the wheel is engaging the floorwhen the shaft is rotated to the second orientation.
 14. A patientsupport apparatus comprising: an elongated base having first and secondends, an upper deck, first and second actuators coupled to the baseadjacent to the first and second ends respectively for movablysupporting the upper deck between a low position and a high position,the first actuator controlling a vertical position of a first end of theupper deck and the second actuator controlling a vertical position of asecond end of the upper deck, an elongated shaft having a longitudinalaxis, the shaft being coupled to the base for movement along thelongitudinal axis, and a foot pedal movably mounted to the base adjacentto the second end thereof, the foot pedal being configured to engage aportion of the shaft adjacent to the second end of the base to move theshaft toward the first end and cause the first actuator to adjust thevertical position of the first end of the upper deck.
 15. The apparatusof claim 14, wherein the shaft is coupled to the base for rotation aboutthe longitudinal axis between a first orientation and a secondorientation, wherein the apparatus further includes a plurality ofcasters rotatably mounted to the base and engaging a floor, and a wheelcoupled to the shaft for movement relative to the base between a firstposition spaced apart from the floor when the shaft is rotated to thefirst orientation, and a second position engaging the floor when theshaft is rotated to the second orientation.
 16. The apparatus of claim15, further including a steering wheel support assembly to couple theshaft to the wheel, wherein the steering wheel support assembly includesa bracket supporting the wheel and pivotally coupled to the base formovement between a first position where the wheel is spaced apart fromthe floor and a second position where the wheel is engaging the floor, aspring biasing the bracket to the first position where the wheel isspaced apart from the floor, and a cam fixed to the shaft and configuredto engage the bracket to cause movement of the bracket to the secondposition where the wheel is engaging the floor when the shaft is rotatedto the second orientation.